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Microstructures and Properties of Three Composites of Alumina, Mullite, and Monoclinic SrAl 2 Si 2 O 8
Author(s) -
Chinn Richard E.,
Haun Michael J.,
Kim Chan Young,
Price David B.
Publication year - 2000
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2000.tb01612.x
Subject(s) - monoclinic crystal system , mullite , materials science , microstructure , composite material , sintering , mineralogy , ceramic , crystallography , crystal structure , chemistry
Three composites that were 96% alumina were mixed and uniaxially dry‐pressed into bars and pellets; all had monoclinic SrAl 2 Si 2 O 8 as an intergranular phase. The diffraction patterns, microstructure, density, dielectric properties, strength, and toughness were measured. The first composition, which contained crystalline SrCO 3 , Al 2 O 3 , and SiO 2 , in a 1:1:2 molar ratio, as the 4% component, densified but was generally inferior to the second and third compositions, which contained strontium aluminosilicate (SrAl x Si y O z , SAS) glass as the 4% component, in terms of mechanical properties, defects, and monoclinic SrAl 2 Si 2 O 8 transformation. The second composition, which lacked B 2 O 3 , was very tough and was comparable to commercial alumina, in terms of the dielectric constant. The third, which contained 0.068% of B 2 O 3 that was dissolved in the SAS glass as a sintering aid, had high strength and toughness and no macroscopically visible defects. Mullite formed, in addition to monoclinic SrAl 2 Si 2 O 8 in all three composites. Alumina–monoclinic SrAl 2 Si 2 O 8 composites of the third composition had room‐temperature properties that were comparable to commercial aluminas that contained 96% alumina and also had potential for mechanical and refractory applications.